I've never had problem with needing a Y cable with portable drives. I've own multiples WD, iOmega and Lacie.
Just the desktop models that needs external AC power adapter that need more than just a single USB 2.0 to get enough power.
If you need a Y adapter to work, then it's most likely the portable drive is poorly designed and/or cheap off-brand or your usb socket is broken.
It could be poor hardware design, too. My friend has an Apple laptop and his WD portable wouldn't work without Y cable. I swapped cable with him since I never needed it.







